Short wave attenuation by a kelp forest canopy

• Published in: Limnology and Oceanography Letters
• Main Authors: M. Lindhart, M. A. Daly, H. Walker, I. B. Arzeno‐Soltero, J. Z. Yin, T. W. Bell, S. G. Monismith, G. Pawlak, J. J. Leichter
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2024
• Subjects: Oceanography; GC1-1581; Sea ice
• Online Access: https://doi.org/10.1002/lol2.10401; https://doaj.org/article/3135f624a9ca4da2a0e3ecd97e310b19

Abstract Giant kelp (Macrocystis pyrifera) forests are common along the California coast. Attached on the rocky bottom at depths of approximately 5–25 m, the kelp, when mature, spans the water column and develops dense, buoyant canopies that interact with waves and currents. We present two novel results based on observations of surface gravity waves in a kelp forest in Point Loma, California. First, we report short wave (1–3 s) attenuation in kelp, quantified by an exponential decay coefficient α∼O10−3m−1—comparable to the dampening effect of sea ice. Second, we identify seasonal and tidal changes in attenuation, peaking mid‐summer with maximum kelp cover, and during low tide when a greater proportion of the fronds are at the surface. Thus, the naturally occurring surface canopies of kelp forests can act as temporally varying, high‐frequency filters of wave energy.